hwset3solution.pdf - 2-4 Solution fc MHz 1 5 a 15 25 30 fIF = 500 kHz fLO(MHz 0.5 1.5 5.5 4.5 15.5 14.5 25.5 24.5 30.5 29.5 fLO(MHz b 1.530.5 0.5-29.5

# hwset3solution.pdf - 2-4 Solution fc MHz 1 5 a 15 25 30 fIF...

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2-4 Solution a. f c MHz f IF = 500 kHz (down-conversion) f IF = 60 MHz (up-conversion) f LO (MHz) f IM (MHz) f LO (MHz) f IM (MHz) 1 0.5 1.5 0 2.0 61 59 121 119 5 5.5 4.5 6.0 4.0 65 55 125 115 15 15.5 14.5 16 14 75 45 135 105 25 25.5 24.5 26 24 85 35 145 95 30 30.5 29.5 31 29 90 30 150 90 b. f LO (MHz) Tuning ratio R = f LO,max /f LO,min 1.5–30.5 20.3 0.5-29.5 59 61-90 1.475 59-30 1.967 c. From the standpoint of easiest and least expensive preselector and LO design, the optimum configuration is up-conversion with high-LO ( f LO tunes over the range 61-90 MHz). This configuration has the smallest tuning ratio ( R = 1 . 475) and all image responses are located well above 30 MHz, which is the upper-cuto ff frequency of the carrier-frequency band of interest. Hence, the preselector can consist of a fix-tuned lowpass filter with cuto ff frequency at 30 MHz. The preselector response should be as small as possible over the range 121-150 MHz in order to provide maximum possible rejection of image responses. 1
2-8 Solution a. 58.6, 80, 278.6, 300, 2520, 2541.4, 2878.6, 2900 MHz b. There would 16 frequencies on the list if there were 4 conversions instead of 3.